Near the end of the 2018 calendar year, the Cardinals signed marquee veteran lefty relief pitcher Andrew Miller to a two-year deal, with a vesting option for a third year if he makes 110 appearances combined in 2019 and 2020. The total money involved for the first two years is close to $25 million, with a few incentive bonuses thrown in as well, and an additional $12 million for the third year. The third year option makes sense on its face. Certainly if Miller makes that many appearances by the conclusion of the 2020 season that would likely be indicative of worthwhile production. (Note: It doesn't always work this way, but with sensible bullpen management it's a decent bet.)
To that point - and this is hardly a secret - worthwhile production from a lefty relief pitcher is something the Cardinals could use. In 2018, their lefty relief core was probably the worst in baseball. With so few effective options, the lefties in the Cardinals bullpen faced the third fewest batters in the National League, too, after the Marlins and the Mets. Because it only makes sense to take the platoon advantage away from the likes of Joey Votto if you have a decent-to-good counter option and the Cardinals didn't have that last season.
And that's too bad, because the Cardinals faced a lot of left-handed hitters in 2018, more than any other team in the NL. Take a look.
Total left-handed batters faced in 2018
It probably wouldn't be a big deal that the Cardinals faced 306 more left-handed hitters than say the Diamondbacks be it not for the aforementioned awfulness of their left-handed bullpen arms. And to understand just how bad they were, here's their production versus left and right-handed hitters when measuring by xFIP.
Total left-handed batters faced by left-handed relief pitchers/xFIP
The Cardinals faced the fourth fewest left-handed batters in the NL with the lefty versus lefty advantage in 2018, and had easily the worst xFIP in the league. We're not dealing with huge samples, but the Cardinals had at least five lefty relief pitchers (Brett Cecil, Tyler Lyons, Tyler Webb, Austin Gomber, and Chasen Shreve, in order of total batters faced) pitch to at least 35 batters in this situation and their xFIPs ranged from 4.29 to 6.35. The NL average in these situations was 3.68.
Total right-handed batters faced by left-handed relief pitchers/xFIP
Same story. When the Cardinals needed to retire a right-handed batter in the later innings of games in 2018 and a lefty was on the mound the results were not pretty. I'm using xFIP because it shows that the Cardinals were rarely striking batters out, and allowed too many walks and balls hit in the air in these situations, but mess around on FanGraphs Splits Leaderboards and use any metric you like and to no surprise the result remains the same: The Cardinals bullpen, particularly the left-handed pitchers, were a disaster in 2018.
Enter Andrew Miller. His story is pretty well known by now but for the uninitiated...he is a former can't-miss starter who did, in fact, miss but he reinvented himself as an elite bullpen arm with the Yankees, and rose to critical acclaim during the 2016 postseason with Cleveland when Terry Francona used him in a fashion most fans dare not dream, which was to use his best bullpen piece in the most crucial of situations to great effect. For such a "well, of course" scenario, it seemed almost radical at the time.
Relevant to this post, and as noted above, Miller is a lefty so the very idea of him on the Cardinals makes a lot of sense. Emphasis on idea because if Miller is no longer effective then it doesn't really matter all that much. And relievers are risky even when coming off their best years. Take Josh Hader. His projections look promising but would it really surprise anyone if 2019 Josh Hader turned out to be a lot different from 2018 Josh Hader?
Well, 2018 Andrew Miller wasn't 2016 or 2017 Andrew Miller. An assortment of injuries, most concerning that to his left shoulder, resulted in an abbreviated season, and decreased velocity and his highest ERA since moving to the bullpen.
Even so, his 2018 version would have been the sharpest knife the Cardinals had in the drawer. At least as far as lefties are concerned. And he still pitched pretty well against left-handed hitters with 49 total batters faced and a 3.51 xFIP, with a strikeout rate over 26 percent. And remove Miller's very last appearance in late September when he allowed four runs in just two-thirds of an inning versus the Royals - which marked just the fourth time all season (34 total appearances) that he allowed more than one run during an appearance - and his ERA drops a full point from 4.24 to 3.24.
The dream is Miller, in his age-34 season, returns to his 2016-2017 form. The realistic goal is that he's healthy and better than his 2018 version which is what Steamer is currently projecting. The "sure, whatever" is that he continues to be what he was last year or even a slightly depleted version of that, which would still be better than the left-handed options the Cardinals had out of their bullpen in 2018. Would that be worth $25 million? I don't know but probably not? Or at least it wouldn't feel that way with recently sunk cost spent on other non-effective relievers, and especially if that money prevents them from pursuing other free agents. But with in-division lefty hitters like Christian Yelich, Joey Votto, Anthony Rizzo, and maybe-but-hopefully-not Bryce Harper, having at least one arm who can reliably retire lefties and turn in a clean inning every now and then is a notable improvement.